Pumping system

ABSTRACT

To draw samples from a source of liquid, a pumping system measures the amount of liquid being pumped by detecting pump cycles and calculating the pumped liquid from this measurement and stored data including conduit size, pressure head and statistical data to correlate detected pump cycles with volume of liquid pumped. Pressure pulses caused by a peristaltic pump are sensed by a piezoelectric film positioned on an inlet conduit connecting the pump to the source of water and, when the liquid reaches a predetermined point determined by the nature of the pulses, the pulses are counted to determine the number of pump cycles.

BACKGROUND OF THE INVENTION

This invention relates to pumping systems and more particularly topumping systems that utilize a pulsating pump to draw samples from asource of liquid.

It is known to pump liquids from a liquid source through a pulsatingpump, such as for example a peristaltic pump, from U.S. Pat. No.4,415,011 to Douglas M. Grant, issued Nov. 15, 1983, and from U.S. Pat.No. 4,660,607 to Carl D. Griffith, issued Apr. 28, 1987. In such aprocess, the water interface in the conduit through which the liquid isbeing pumped is sensed to provide an indication of where the liquid isin the conduit.

Several different sensing mechanisms have been utilized in such pumpssuch as an optical sensing mechanism, a capacitance sensing mechanismand a electrical conductivity sensing mechanism. The information aboutthe sensed interface is utilized together with other information tometer a fixed volume of liquid into one or more sample containers. U.S.Pat. No. 4,415,011 discloses the metering of liquid by counting cyclesof the pump from the shaft of the pump.

In the prior art apparatus, the sensors are either internal or externalto the conduit and utilize several different arrangements such as bysensing a change in capacitance between two electrodes outside theconduit as the liquid interface passes through or by sensing changes inthe absorption of light transmitted through the conduit or changes inelectrical conductivity.

These prior art pumps and sensing mechanisms have several disadvantagessuch as for example: (1) under some circumstances, the sensing mechanismmay have difficulty in distinguishing between a continuous flow of theliquid and spurts of liquid that may be splashed through the sensingpoint; (2) the pump may slow due to battery drain or other unexpectedeffects; (3) the head of water may suddenly change, causing variationsin pumping; or (4) conductivity and capacitive sensors are prone tomalfunctions caused by bridges and changes in the conductivity ofliquids.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a novel pumpingsystem.

It is a further object of the invention to provide a pumping systemwhich senses the location of liquid being pumped in a conduit by changesin force caused by the pumping.

It is a still further object of the invention to provide a pumpingtechnique which is controlled in accordance with pulses caused by apulsating pump.

It is a still further object of the invention to provide a pumpingsystem which utilizes stored statistical data along with otherinformation relating to the head of pressure and size of conduits tomeasure the amount of liquid being pumped.

It is a still further object of the invention to provide a novel pumpingtechnique in which a combination of measurements of cycles of the pumpand stored data is used to meter the amount of liquid being pumped.

It is a still further object of the invention to provide a novel pumpingtechnique for metering the amount of liquid being pumped by storedstatistical data relating the cycles of the pump to pressure head andflow of liquid, and other information such as that relating to conduitsize and the like.

It is still another object of the invention to provide a liquid meteringpump that uses detected pump cycles and stored data including conduitsize, and pressure head to correlate detected pump cycles with volume ofliquid pumped.

In accordance with the above and further objects of the invention, apumping system includes: (1) a pump that creates pressure pulses as itpumps; (2) a conduit through which liquid is drawn; (3) a samplecontainer; and (4) a sensor for sensing pulses in the conduit. Thesensor is positioned at a location along the conduit where it generatesa signal related to pressure or force in the conduit. In the preferredembodiment, it is a piezoelectric film which senses motion of theconduit as it attempts to expand because of force generated by the pumpsuch as the back pressure in the liquid caused by reaction to backedinertia of moving water when a pump roller closes the conduit againstfurther flow.

In the operation of the sensor, the sensor generates electrical signalsindicating pulses caused by the pump. Signals generated at the time thatthe liquid reaches a predetermined point are distinguished from otherpulsations to indicate the interface of the liquid. Pulses are countedand when there are interruptions in the count, a standard criteria isapplied to determine if the interruption is because the initialindication of an interface of liquid was false and only caused bysplashing or surging or the like or whether it was a genuine interfaceand the lapse in pulses was an error. Pulses are added which indicatethat the liquid is indeed flowing beyond a predetermined point.

To determine when a predetermined amount of liquid has been deposited ina container, the length of conduit, inner diameter of conduit and thelike are measured, and in the preferred embodiment, entered into thememory of a microprocessor. A statistical base determined over a numberof runs is utilized so that when the interface of the liquid isdetected, the number of counts of the pump motor before the interfacereaches a predetermined location is used as an indication of the head ofwater pressure by statistically relating it in a look-up table.

The head of pressure is then utilized together with the known lengthfrom the interface to the sample collector to determine how many cyclesof a pump are required to meter approximately the right amount of liquidinto the container in the sample collector. The number of cycles isdetermined from a statistical base in a look-up table which is correctedfor the characteristics that affect pulse counts such as drag, head ofpressure, cross-sectional area of conduit, length of conduit, or thelie.

When the preset volume of liquid as determined by the number of pumpingcycles has been deposited in the container, the pump reverses directionto purge the tube and prevent further liquid from being deposited intothe container. This cycle may be repeated manually or automaticallyunder the control of a microprocessor with alternate purge and fillingcycles in a manner long used in the art.

With the liquid sensor, rinse cycles can be performed in which theliquid can be drawn to a more precise point than in prior art apparatusso as to better clean the conduit. With this combination, a rinse mayencompass a large portion of the conduit without causing liquid to flowinto a sample container. The rinse liquid can be drawn even to thehighest point in the conduit downstream of the pump with safety but inthe preferred embodiment it is stopped at the inlet of the pump.

In the preferred embodiment, the interface of the liquid is determinedby a change of measured amplitude in the pulses generated by the strainsensitive piezoelectric film. This change in amplitude occurs if thesensor is positioned on the inlet side of the pump when the liquidapproaches the pump. Force pulses are created by: (1) inertia because ofchanges in momentum from blocking the liquid by closure of the conduitin which liquid is flowing by a roller; and (2) other forces such asroller pressure transmitted through the liquid or tube wall. It occursat a point because there is a cushion of air between the sensor and thepump that attenuates the pulse. If the sensor is located on the outletside of the pump, the change in amplitude occurs when the liquid reachesthe sensor.

In the preferred embodiment, once the pumping system has determined thatliquid is flowing from the amplitude of measured pulses, sensed cyclesof the pump are counted during the time the amplitude of the strainpulses is above the threshold.

From the above description, it can be understood that the pumping systemof this invention has several advantages, such as for example: (1) itmore precisely meters the amount of liquid because it is based onpulsations and pump cycles and reacts to the head of pressure; (2)measurement is made using a criteria which is not altered by splashingor surging of the water or the light transmission characteristics of anoptical path or the capacitance or other noise effects that has causeddifficulties with other types of sensors; and (3) the metering criteriais partly determined by a statistical base to compensate more readilyfor unpredicted variations between samples; and (4) the sensor is notwetted by the pumped liquid.

SUMMARY OF THE DRAWINGS

The above noted and other features of the invention will be betterunderstood from the following detailed description when considered withreference to the accompanying drawings, in which:

FIG. 1 is a block diagram of a pumping system in accordance with theinvention;

FIG. 2 is a partially exploded, perspective view of a liquid sensingdevice used in the embodiment of the invention shown in FIG. 1;

FIG. 3 is an exploded perspective view of a liquid sensing device usedin the embodiment the invention shown in FIG. 1;

FIG. 4 is an elevational sectional view of a portion of a liquid sensingdevice used in the embodiment of the invention shown in FIG. 3;

FIG. 5 is a fragmentary, exploded perspective view of the liquid sensingdevice and pumping system used in the embodiment of the invention shownin FIG. 1;

FIG. 6 is a block diagram of a portion of the pumping system of FIG. 1;

FIG. 7 is a block diagram illustrating a process used in the pumpingsystem of FIG. 1;

FIG. 8 is a flow diagram of a program used in the embodiment of FIG. 1;

FIG. 9 is a block diagram of a portion of one of the embodiments of FIG.8;

FIG. 10 is a flow diagram of a portion of the embodiment of FIG. 9;

FIG. 11 is a flow diagram of another portion of the embodiment of FIG.9;

FIG. 12 is a flow diagram of still another portion of the embodiment ofFIG. 9;

FIG. 13 is a block diagram of still another portion of the embodiment ofFIG. 9;

FIG. 14 is a block diagram of another portion of the program of FIG. 8;

FIG. 15 is a flow diagram of a portion of still another embodiment theprogram of FIG. 8;

FIG. 16 is a flow diagram of a portion of the program segment of FIG.15;

FIG. 17 is a block diagram of still another portion of the embodiment ofFIG. 8; and

FIG. 18 is a block diagram of another embodiment of FIG. 10.

DETAILED DESCRIPTION

In FIG. 1, there is shown a block diagram of a pumping system 10 havinga flow measurement and control circuit 12, a pulse sensor assembly 14, aperistaltic pump 16, a cycle signal generator 11 for generating signalsindicating the cycles of the pump, a sample collector 18 and a conduit20. The conduit 20 is fastened to and communicates with an inletstraining device 22 and extends through the pulse sensor assembly 14,the peristaltic pump assembly 16 and the sample collector 18 into whichit supplies liquid.

The flow measurement and control circuit 12 is electrically connected tothe pulse sensor assembly 14 to receive signals therefrom indicatingpumping cycles of liquid after the liquid has reached a specificlocation and to control the peristaltic pump assembly 16 and samplecollector 18 to deposit predetermined volumes of liquid into a samplecontainer or a group of sample containers in accordance with apreprogrammed procedure or under the manual control of an operator.

The cycle signal generator 11 is connected to the rotor of theperistaltic pump in the peristaltic pump assembly 16 and generates apredetermined number of pulses for each cycle. These pulses aretransmitted to the flow measurement and control circuit 12 through aconductor 13 to provide an indication of pump cycles and throughconductor 15 to indicate the direction of rotation (necessary only inone embodiment) for use in controlling the peristaltic pump assembly 16in a manner to be described hereinafter.

The conduit 20, inlet strainer 22, peristaltic pump assembly 16 andsample collector 18 may be of any suitable type. A similar arrangementis disclosed in U.S. Pat. No. 4,415,011 except that the samplecollecting arrangement of U.S. Pat. No. 4,415,011 utilizes a differenttype of pulse sensor and relies for control of the volume of liquid on adifferent circuit arrangement and program. Nonetheless, many differentcontrol circuits and different types of pumps which produce pulses whenthey are pumping, types of sample collector 18, inlet strainer 22 orconduit 20 may be used in the invention.

In use, the inlet strainer 22 is inserted in the liquid 24, samples ofwhich are to be drawn and data such as the amount of fluid for eachsample, the time between samples, the size of the conduit 20 and thelike are entered through a keyboard. The peristaltic pump assembly 16 isstarted under the control of the flow measurement and control circuit 12and begins pumping liquid. As it pumps liquid, there is some forceapplied to the flexible conduit 20 as the liquid 24 begins to moveupwardly through the pulse sensor assembly 14 into the peristaltic pumpassembly 16.

The pulse sensor assembly 14 senses pulses, and for this purpose is, inthe preferred embodiment, a piezoelectric film contacting the conduit tosense expansion of the conduit. A suitable type of film is availablefrom the Kynar Piezo Film Sensor Division of Pennwalt Corporation havingan office at 950 Forage Avenue, Norristown, Pa. 19403. This film isdescribed in a booklet entitled "Piezoelectric Film Sensors AnIntroduction to the Techology", by Douglas Kehrhahn, available fromPennwalt Corporation, Piezo Film Sensor Division, P.0. Box 799, ValleyForge, Pa. 19482.

Because the pulsations from the peristaltic pump assembly 16 areabsorbed by air in the conduit 20 until the liquid reaches theperistaltic pump assembly 16, the pulses received by the pulse sensorassembly 14 do not cross a predetermined amplitude threshold until theliquid reaches a predetermined location. This predetermined locationdepends on the size of the head and the amount of the liquid beingpumped. The greater the head, the closer the predetermined location isto the pump. It is possible to locate the sensor directly at the pump orafter (downstream of) the pump and this will change the location of thepredetermined point. Data in the lookup table must be adapted to thischange in location of the sensor.

With this arrangement, the pulse sensor assembly 14 senses pulseamplitude and determines the interface of pulses and applies the signalto the flow measurement and control circuit 12 indicating that theliquid has reached the predetermined location between the peristalticpump assembly 16 and the sample collector 18. At this point in time, theflow measurement and control circuit 12 may, in accordance with somestandard programs, purge the conduit and redraw the fluid 24, or inothers, continue to pump to draw a sample and deposit the sample into acontainer.

When the location of the fluid 24 reaches the sensor after a purge cycleif there is one, the flow measurement and control circuit 12 causes apredetermined amount of fluid to be deposited in a container within thesample collector 18, and in some embodiments, the sample collector mayinclude a distributor or may move containers to deposit sample insuccession during different pumping cycles. The number of pumping cyclesrequired is determined in the preferred embodiment by a computer look-uptable containing data based on trial and error measurements withconduits of the same inner diameter to determine the number of pumpingcycles required for a given volume once the interface has been sensed ina manner to be described in greater detail hereinafter.

The statistical database and look-up tables can be calibrated andcontinuously updated by standard adaptive techniques. More specifically,the amount of sample deposited in containers can be measured and enteredinto the database to update the look-up table by providing a betteraverage base for the variable parameters.

The sensor may sense some initial bursts of liquid prior to a constantcontinuous flow. This happens because the sensor detects an initial flowof liquid but in some circumstances, the fluid 24 drops away from thepump and has to be pulled back to the pump. The fluid measurement andcontrol circuit 12 counts the number of cycles of the pump as indicatedby the cycle signal generator 11 for the liquid that flows through apredetermined point and adds those cycles that are significant to thetotal liquid pumped into a sample container or to a predetermined pointrequired for a rinse or purge cycle. The counting occurs after theliquid interface reaches the predetermined point. This permits thepumping system to more precisely meter liquid into a container.

In FIG. 2, there is shown a partly exploded perspective view of thepulse sensor assembly 14 having first and second sections 30 and 32. Thefirst and second sections 30 and 32 fit together to form an enclosurehaving two cylindrical openings extending through it, each of whichreceive and confine a different part of a length of conduit 20.

One part of the length of the conduit 20 fits in a first groove 45 whichreceives the conduit 20, with a piezoelectric sensor (not shown in FIG.2) fitting over it to be strained as the conduit 20 deforms. The conduit20 is looped through the pump and passes in the other direction througha second cylindrical groove. The two sections are held together byfasteners 34A, 34B

In FIG . 3, there is shown an exploded perspective view of the secondsection 32 having a housing 35, a piezoelectric sensor 42, a wovenfiberglass protective member 37 and first and second pin seating inserts38A and 38B. The housing 35 of the second section 32 receives theprotective member 37, piezoelectric sensor 42, and inserts 38A and 38Band forms a unit fastened together with first section 30 to hold theconduit 20 (FIGS. 1 and 2) against motion caused by the pump 16 (FIG. 1)during its rotation against the conduit 20 and to hold and protect thepiezoelectric sensor 42 against the conduit to sense changes in pressurewithin it caused by action of the pump.

The housing 35 includes: (1) five apertures 33A, 33B, 33C, 33D and 33Esized to receive one end of five fasteners 36A, 36B, 36C, 36D and 36E;(2) four smaller apertures 39A, 39B, 39C and 39D which receive one endof four pins 41A, 41B, 41C and 41D that pass through apertures 43A, 43B,43C and 43D in the piezoelectric sensor 42, and form a part of theholding means for the sensor 42; (3) cylindrical grooves 45 and 47 and asensing aperture 47A through which the conductor 46B passes. With thisarrangement, the housing 35 aids in holding the sensor 42, theprotective member 37 and the inserts 38A and 38B in place. The firstsection 30 and second section 32 (FIG. 2) of the sensor assembly areheld together by thumb screws 34A and 34B (FIG. 2) which engage threadedbores 29A and 29B. The fasteners 36A-36E thread into bosses (not shown)in the inserts 38A and 38B.

The piezoelectric sensor 42 includes: (1) a piezoelectric film 46A whichchanges its electrical characteristics in response to changes in itsstrain and generates an electrical potential; and (2) a conductor 46Bconnected to the film which passes through the second section 32 forelectrical connection to the flow measurement and control circuit 12(FIG. 1) to which it transmits electrical signals indicating changes inthe strain in the piezoelectric film 46A. The piezoelectric film 46Aincludes four apertures 43A-43D passing through it on opposite sides ofthe groove 45 to form a portion of a holding or clamping means holdingthe piezoelectric film 46A in place against the conduit 20 (FIG. 1 and2).

During installation of the tubing 20, the piezoelectric film 46A ispre-stretched by the force of the tubing against the piezoelectric film46A, the edges of which are held by the pins 41A-41D. The contactbetween the tubing 20 and the piezoelectric film 46A is maintainedintimate by the bias from the stretching of the piezoelectric film 46Aand extends over a sufficient surface area with sufficient pressurebetween the film and the tube 20 to supply adequate coupling for areliable transfer of force. The coupling is adequate to cause the filmto generate repeatable electrical signals in response to a range offorces transferred to it. In the preferred embodiment the area ofcontact between the piezoelectric film 46A and the tube 20 is 1/4 squareinch but can be as small as 1/16 square inch.

To protect the piezoelectric sensor 42, a woven fiberglass member 37with a Teflon (trademark by Du Pont de Nemours, E.I. and Co.,Wilmington, Del. 19898 for tetrafluoroethylene fluorocarbon polymers)coating on its top and bottom surfaces and fused over it to form astrong flexible member. It also includes: (1) five apertures alignedwith the five apertures 33A, 33B, 33C, 33D and 33E in the housing 35 toreceive the two bosses in 38A (not shown) and three bosses in 38B (notshown) that the fasteners 36A, 36B, 36C, 36D and 36E are threaded into;(2) an aperture aligned with the aperture 29A in the housing 35 to holdfirst section 30 and housing 35 together; and (3) four apertures 45A-45Daligned with the four smaller apertures 39A, 39B, 39C and 39D to receivefour pins 41A, 41B, 41C and 41D that are also received by apertures 43A,43B, 43C and 43D in the piezoelectric film 46A before being seated inthe inserts 38A and 38B.

To receive and hold one end of the pins 41A-41D, the inserts 38A and 38Bare sized to rest between the protective member 37 and the first section30 (FIG. 2) and includes: (1) an aperture to receive fastener 34A (FIG.2) which passes through it and engages threaded bore 29A; and (2) fourholes 37A-37D in the side facing the protective member 37 to receive oneend of each of the corresponding pins 41A-41D. With this arrangement,the pins 41A-41D hold the film 46A in place on opposite sides of theconduit 20 (FIG. 2) and are in turn held in place by the inserts 38A and38B on one side and the housing 35 on the other.

In FIG. 4, there is shown an elevational sectional view of the secondsection 32 taken through lines 4--4 of FIG. 3 and showing the grooves 45and 47, apertures 29A, 29B, 39D, 39E, 33B, 33C, 33D for seating pins andholding the first and second sections together. As best shown in thisview, the conduits and piezoelectric sensor may be securely held in theformed solid rigid housing to receive signals from the pump. Within thegroove 45 there is an enlarged portion 45E (FIG. 3) to allow expansionof conduit 20 during pulsation. The opening 47A is potted to avoid wireflexing.

In the preferred embodiment, the enlarged portion 45E of the groove 45is a large enough area to receive the conduit 20 and piezoelectric film46A and forms a recess with a depth approximately 1/16 inch. It is largeenough to accommodate expansion of the conduit 20 during pulsation andthe depth should be at least the thickness of the film plus oneone-thousandth of an inch.

In FIG. 5, there is shown a simplified view of the peristaltic pumpassembly 16 and sensor assembly 14. As shown in this view, the sensorassembly 14 is on the inlet side of the peristaltic pump assembly 16 andin one embodiment spaced therefrom. In the preferred embodiment, thedistance between a roller 21 as it contacts tube 20 and the sensorassembly 14 is 3.125 inches and should be less than 18 inches to avoidundue attenuation of the pulses imported through the conduit and liquidfrom the force of pumps to the sensor assembly 14 before being sensed.Although the embodiment of FIG. 5 shows a sensing assembly 14 spacedfrom the rollers 21 of the pump, it is possible to locate apiezoelectric film in the pump housing positioned to sense therelaxation of the conduit 20 between compression by rollers. This willresult in a change in strain within the piezoelectric film 46A. Thechange in strain will have a different time-amplitude characteristicwhen liquid is in the pump than when it has not yet reached the pump orhas passed through the pump.

In FIG. 6, there is shown a block diagram of the flow measurement andcontrol circuit 12 having a microprocessor 62 and an interface assemblyshown generally at 60. In the preferred embodiment, the microprocessor62 is a Model 64180 sold by Hitachi America, Ltd., Software Sales andSupport Division, 950 Elm Avenue--No. 100, San Bruno, Calif. 94066, andincludes a look-up table memory 63 as well as the normal logiccomponents 65 forming the microprocessor central control. The softwareused in the preferred embodiment is attached hereto as attachment A. Thelook-up table memory 63 is accessed by the central control to look-upvalues corresponding to certain numbers of cycles of the pump 16(FIG. 1) applied to it through the pump interface 60 through a conductor77.

The interface 60 includes a sensor interface 70, connected to the pulsesensor assembly 14 (FIG. 1) through a conductor 46 and to themicroprocessor 62 through a conductor 67, a keyboard 72 for enteringdata into the microprocessor 62 through a cable 72A, a pump interface 74for transmitting start and stop signals through a cable 75 to theperistaltic pump assembly 16 (FIG. 1) in response to signals from themicroprocessor 62 through a conductor 77 and a sample collectorinterface 76 receiving signals from the sample collector 18 (FIG. 1) ona conductor 79 and transmitting signals to the sample collector 18through a conductor 81. The sample collector interface 76 transmitsignals to the microprocessor 62 through a conductor 82 and receivessignals through a conductor 84.

With this arrangement, the microprocessor receives indications ofcycling of the peristaltic pump assembly 16 when the water interfacereaches a predetermined location, counts those cycles and uses the countfor other control functions such as moving bottles in the samplecollector, stopping and reversing the pump and restarting the pump foranother cycle, starting timing for the intervals between drawing samplesand the like.

In the preferred embodiment, once the pumping system has determined thatliquid is flowing from the amplitude of measured pulses, sensed cyclesof the pump are counted during the time the amplitude of the strainpulses is above the threshold.

In FIG. 7, there is shown a block diagram of the sensor interface 70having an input low-pass filter and pulse shaping section 71 and anoutput section 73. The input low-pass filter 71 is a National MF6 set tohave a 45 hertz cut-off and a 0.5 volt threshold. The output section 73shapes the input pulses to a square wave and discriminates againstpulses having a time duration less than a predetermined time set by theRC circuit 73A. However, any suitable interface may be used.

In FIG. 8, there is shown a block diagram of the main subprograms of theprogram that controls the pumping system 10 (FIG. 1) including a standbymode subprogram 140 and a plurality of operating subprograms showngenerally at 141. When the pumping system 10 is turned on and aftercompletion of each of the operating subprograms shown collectively at141, the program automatically goes to the standby mode 140. The userthen enters the command to go to any of the other subprograms of thepumping system 10 (FIG. 1). The main subprograms shown in the group 141include: (1) configure sequence 150; (2) program sequence 190; (3)manual controls 200; (4) run program 210; and (5) program and runtimereview 220.

Many programs used in the operation of a pumping system are not relatedto the invention and are standard for equipment of this type. Theseprograms are not described in any detail herein. However, the programsrelated to the invention are described in flow diagram form below and acomputer printout of the code is made a part of the specification asattachment A.

Before starting the pump, the user may enter data to set up the pumpingsystem 10(FIG. 1) so that it will operate to the user's specific needs.If the user does not wish to change the settings from the most recentrun, then he would not use these programs. This user-defined informationmay be entered in the configure sequence 150 and the program sequence190. The configure sequence 150 is used to enter certain data such asbottle count and size, correct time and suction line information. Mostof the data entered in the configure sequence 150 are of a type that donot change often. The program sequence 190 is used to enter data for thespecifics of the sampling routine such as sample volume, frequency anddistribution method.

The run program sequence 210 runs the sampling routine using the dataprogrammed in the configure sequence 150 and program sequence 190 andthe program and runtime review 220 displays the program settings andsampling routine results. The manual controls program sequence 200sequences through steps that operate the pump and distributor inresponse to manually entered instructions by the operator.

In FIG. 9, there is shown a block diagram of the main parts of theconfigure sequence 150 (FIG. 8). The parts include: (1) tubing lifeindicator subsequence 154; (2) liquid detector subsequence 162; (3)suction line subsequence 172; and (4) bottle subsequence 180. Thesubsequences together provide data points into the system forconfiguring the pumping system 10 (FIG. 1).

In FIG. 10, there is shown a flow diagram of the tubing life indicatorsubsequence 154 (FIG. 9) of the configure sequence 150 (FIGS. 8 and 9).The tubing life indicator subsequence 154 monitors usage of the tubing20 by keeping track of how many cycles the pump has made against thetubing 20 in any direction since its last replacement and warns the userthat the tubing 20 should be replaced. Included in the tubing lifeindicator subsequence 154 are: (1) a pump counter subsequence at 156;(2) a reset pump counter subsequence at 158; and (3) a warning trippoint subsequence at 160.

The total pump strokes (12 for each revolution of the pump) and thepoint at which the counter warns the user that it is time to change thetubing 20 are displayed to the user at 156. The range of pump counts forthe life of the tubing 20 is usually between 50,000 and 2 million pumpcounts. If the tubing 20 has been replaced, the user would indicate yesin the reset pump counter subsequence 158 to reset the pump countersubsequence 156. The user-defined warning trip point is entered insubsequence 160. While the pump is pumping, the total pump counts areupdated in a counter and compared to the user-defined count. When theupdate count exceeds the user-defined count, a warning is given.

In FIG. 11, there is shown a flow diagram of the options for the liquiddetector subsequence 162 (FIG. 9) of the configure sequence 150 (FIGS. 8and 9). The liquid detector subsequence 162 controls the liquid detectorand related settings and how many times it will be used to detectliquid. The options for the liquid detector subsequence 162 include: (1)an enable/disable liquid detector subsequence 164; (2) a rinse cyclesubsequence 166; (3) a manual head subsequence 168; and (4) a retrysubsequence 170.

If operation of the detector is ever questionable, the user can disableit at 164. However, if the detector is disabled, the head is entered inthe programming sequence 190 (FIG. 8).

To detect the liquid either in the rinse cycle or during collection ofthe sample, if the detector is enabled in 164, then the program requeststhe user to specify: (1) the number of rinse cycles in the rinsesubsequence 166; (2) whether a head will be entered manually in themanual head subsequence 168; and (3) the amount of retries in the retrysubsequence 170. The retry subsequence 170 controls the amount ofretries for both the rinse cycles and the actual collection of sample ifno liquid is detected during either process.

In FIG. 12, there is shown a flow diagram of the suction linesubsequence 172 (FIG. 9) of the configure sequence 150 (FIGS. 8 and 9).The suction line subsequence 172 is used to gather informationconcerning the suction line, generates the look-up tables and sets thenumber of post-purge counts. The subsequences in this program are: (1)the inner diameter subsequence 174; (2) the material subsequence 176;and (3) the length subsequence 178.

In the preferred embodiment, the inner diameter of the suction lineentered in the subsequence 174 is entered in inches such as one-quarterinch or three-eighths of an inch, the choice of suction line entered inthe material subsequence 176 is either vinyl or Teflon and the length ofthe suction line entered in the length subsequence 178 can be betweenthree and ninety-nine feet.

In FIG. 13, there is shown a flow diagram of the bottle subsequence 180(FIG. 9) of the configure sequence 150 (FIGS. 8 and 9). The bottlesubsequence 180 is used to set maximum sampling volumes and provideinformation to the distributor movement routine.

Two of the subsequences included in the bottle subsequence 180 arebottle number subsequence 182 and bottle volume subsequence 184. Thebottle number subsequence 180 is used to enter the amount of bottles inthe base and the bottle volume subsequence 184 is used to enter themaximum volume of liquid to be inserted into each bottle.

In FIG. 14, there is shown a flow diagram of portions of the programsequence 190 (FIG. 8). The program sequence 190 is for enteringspecifics of a sampling routine which include: (1) the bottles persample subsequence 192; (2) the sample volume subsequence 194; and (3)the head subsequence at 196. The number of bottles per sample is enteredin the sample subsequence 192 and the amount of sample to be distributedinto each bottle is entered in the sample volume subsequence 194.

To ensure a more accurate calculation of the pump count maximum or ifthe liquid detector was disabled, the suction head is entered in thehead subsequence 196. The suction head is used if the liquid detectorwas disabled at 164 in the liquid detector subsequence 162 or the userindicated in the head subsequence 168 that a head would be manuallyentered (FIG. 11). In the preferred embodiment, the user can enter aminimum volume of sample of 10 milliliters and a minimum suction head ofone foot.

In FIG. 15, there is shown a flow diagram of a portion of the runprogram sequence 210 for drawing and distributing a sample in accordancewith an embodiment of the invention. The run program sequence 210includes: (1) the series of steps 92 relating to starting the pump; (2)the rinse routine 100; (3) the series of steps 108 relating to drawing asample; (4) the series of steps 114 relating to distributing the sample;(5) the series of steps 122 relating to storage of the samplinginformation; and (6) the step 128 of retrying a rinse routine or pumpsample routine.

The series of steps 92 relating to starting the pump include the step 94of receiving the sample command, the step 96 of calculating the maximumpump count and the pre-sample purge step 98. After the sample command 94has been received, a maximum pump count is calculated based on the headentered in the head subsequence 196 (FIG. 14) or the head from theprevious sample if no head was entered. Only one value for the head isused to calculate the maximum pump counts and is used throughout theprogram segment. The pre-sample purge command 98 is then performed toclear the strainer of any debris which may have collected since the lastsample was taken.

After the pre-sample purge is completed, the rinse routine 100 isactivated which includes the step 102 to determine if a rinse should beperformed or if a second or third rinse should occur. Rinse routineshave already been preprogrammed by the user in the rinse subsequence 166(FIG. 11). If a rinse is programmed, the liquid is pumped forward in thestep 104 until a predetermined amount of liquid is detected in step 107and the liquid is purged in the step 106.

If the predetermined amount of rinse liquid is detected as havingreached its destination, the rinse routine 100 is begun again asindicated at 102. If another rinse routine is remaining, the liquid ispumped forward at 104 and the remaining steps of the rinse routine arecarried out. The rinse routine 100 is repeated until there are nofurther rinses. When the rinses are complete, the series of steps 108relating to drawing a sample continues with the pump sample routine 110and the step 112 of detecting the liquid.

If no liquid was detected during the rinse routine 100 in the step 107or the step 112 of the series of steps 108, the program in the step 128accesses the retry subsequence 170 of the liquid detector subsequence162 (FIG. 11) to find out if it should retry pumping sample beforeshutting down. If the user entered any retries, and the total amount ofretries has not been met, the program returns to the pre-sample purge 98and starts the rinse routine 100.

If all of the retries have been made or if no retries were programmed,the controller performs a post sample purge at 123, stores the samplinginformation at 124 and returns to the calling routine at 126 of thesteps 122.

If a rinse routine 100 was not programmed, the steps 104, 106 and 107are skipped and the program goes directly to drawing a sample at 110 anddetermines if liquid is detected at 112. The pump sample routine 110 isthe actual process of drawing and measuring the sample and will be laterdescribed in more detail.

When it is indicated at 112 that liquid was detected, the series ofsteps 114 relating to distributing a sample is performed. The first stepof the series of steps 114 is the step 116 of determining if sample isto be inputted into one or more bottles. If only one bottle will befilled, a user-defined amount of sample is then emptied into the bottle,a post sample purge is performed at 123, the sampling information isstored at 124, and the program returns to the calling routine at 126 inthe series of steps 122.

If there is more than one bottle to be filled, a short purge 118 is madeto back the liquid up so that it can detect a second user-defined amountof sample and the distributor is moved to the next sample bottle at 120.

The program segment 210 then returns to the pump sample routine 110until data is received at 112 that the user-defined amount of liquid isdetected. The program checks whether there is more than one bottle leftto fill at 116 and then empties the sample into a sample bottle. If moresample is needed, the remaining steps, 118 of purging the sample and 120of moving the distributor to the next bottle are repeated again. Thesteps of emptying the sample into the bottle at 116, purging the liquidat 118 and moving the distributor at 120 are repeated until it isindicated at 116 that no more sample will be distributed. When no moresample is needed, a post sample purge is performed at 123, the samplinginformation is stored at 124, and the program returns to the callingroutine at 126 in the series of steps 122.

In FIG. 16, there is shown a flow diagram of the pump sample routine 110of the program segment 210 (FIG. 15) for drawing and distributing asample. This routine is the actual pumping of the sample to collect apredetermined amount of liquid in a sample bottle. The pump sampleroutine 110 includes: (1) the series of steps 131 relating to thebeginning stages of pumping; (2) the series of steps 139 related toobtaining the water count; (3) the step 151 of saving information thatno liquid was detected; and (4) the series of steps 153 of stopping thepump.

In the series of steps 131, a pump sample command is received at 137 andthe sample is pumped upstream through the tubing 20 (FIGS. 1, 2 and 5).The sample is then continually pumped and the program waits for a pumpcount change at 133. The maximum pump count was predetermined based onthe head of the previous sample or measured by the user and entered intothe program before the user began the pump (not shown) in the configuresequence 150 (FIG. 8).

The program 110 then goes through a series of steps at 139 starting withdetermining if the maximum pump count has been exceeded in the step 161.If the maximum pump count has been exceeded, the program will save theinformation indicating that no liquid was detected at 151 and proceed tothe series of steps 153 of stopping the pump. During shutdown of thepump, the program shuts the pump off at 155 and returns to the callingroutine at 157.

If the maximum pump count has not been exceeded at 161, it is thendetermined whether a good water count was found at 143. The programdetermines if a water count is received so near to the beginning of asample drawing run as to indicate an error. This can occur in the firstfew cycles such as for example four cycles of the pump. After apredetermined number of cycles of the pump, this type of error tends notto occur. In the preferred embodiment, the pump must have counted atleast 50 counts before the count is considered good. If it was not agood water count, the program: (1) returns to waiting for the pump countat 133; and (2) maintains in memory the amount of water counts alreadyreceived and adds a new water count to the previously received watercounts.

If it was a good water count, it is then determined if a new maximumamount of water counts should be calculated at 145. If a new maximumshould be made, the program calculates a new maximum water count at 149,using the head from the previous sample or the head defined by the userin the head subsequence 196 (FIG. 14), and then decides at 147 if thesample water count is the correct amount. If not enough sample waspumped, the program returns to wait for the pump count at 133 and pumpsmore liquid until it has pumped a predetermined amount of pump countsand continues with the series of steps 139 starting at 161 to determineif the maximum count was exceeded. If the pump did receive a correctwater count, it is recorded in memory at 159 that the sample volume wasdelivered correctly and proceeds with the series of steps 153 ofshutting down the pump at 155 and returning to the calling routine at157.

If it is not necessary to calculate the maximum water count, then theprogram skips the step 149 and determines at this point if it is acorrect water count at 147, records that the sample volume was deliveredcorrectly at 159 and proceeds with the series of steps 153 of shuttingoff the pump at 155 and returning to the calling routines at 157.

When the program returns to the calling routine at 157, the memory isaccessed to find out if the liquid was detected at 112 (FIG. 15) and ifit was not, the program would advance to the program at 128 to access170 of the options for the liquid detector control 162 (FIG. 9) of theconfigure sequence 150 to find out if it should retry pumping samplebefore shutting down. If the user entered any retries, and the totalamount of retries has not been met, then the program returns to purgingthe pre-sample at 98 and continuing with the rinse routine 100 (FIG.15).

In FIG. 17, there is shown a flow diagram of the program and run reviewsequence 220 (FIG. 8). The program and run review sequence 220 is usedto check program setting or sampling routine results. The subsequencesincluded are the pump tubing warning subsequence 222 and the sampleinformation for the last sample routine subsequence 223.

Each time the pump count maximum for replacing the tubing is exceeded,the pump tubing warning message at 222 is displayed. The threshold forthe pump count maximum has been user-defined in the tubing lifeindicator control 154 at 156 (FIG. 10) before beginning the pump. If theuser does not enter a new threshold, the threshold from the previoussampling process will be used.

After each sample gathering process, certain information is stored inmemory for future use at 223. Included are: (1) if the sample processwas performed and no liquid was detected at 224; (2) the time and dateat 226; and (3) the number of pump counts before liquid was detected at228 and the amount of time for the entire pump cycle. The number ofcounts before liquid was detected at 228 is used to calculate the headat 149 (FIG. 16).

In FIG. 18, there is shown a block diagram of another embodiment oftubing life indicator circuit 154A for providing a signal after apredetermined number of strokes of roller against the tube 20 (FIGS. 1,2 and 5) in the peristaltic pump assembly 16 (FIG. 1), having the cyclesignal generator 11, a counter 240, a switch 246, a manually resettableswitch 242 and a warning light 252. The counter 240 is directlyconnected to the conductor 13 to receive all counts regardless ofdirection and having an output set at a predetermined number of countsconnected to the resettable switch 242 to actuate the switch at thepredetermined number of counts and thus energize the warning light towhich it is connected.

With this arrangement, the operator may set the counter 240 at a countthat indicates the tube 20 (FIGS. 1, 2 and 5) should be replaced. Whenthe number of pulses from the cycle signal generator 11 reaches thepreset number, the counter 240 supplies a signal to the resettableswitch 242 which applies a signal from the source of voltage 254 to thewarning light 252. The resettable switch 242 can be manually reset whenthe tube is changed and it resets the counter 240 and disconnects thepower 254 from the warning light 252.

To permit a hardware determination of the direction of rotation, theswitch 246 receives pulses from the conductor 13 and a direction signalfrom the cycle signal generator 11 to switch from one of the two outputconductors 248 or 250 to the other so that pulses representing thenumber cycles in each direction can be determined. This function canalso be performed in software.

From the above description, it can be understood that the pumping systemof this invention has several advantages, such as for example: (1) itmore precisely meters the amount of liquid because it is based onpulsations and pump cycles which react to the head of pressure; (2)measurement is made using a criteria which is not altered by splashingor surging of the water or the light transmission characteristics of anoptical path or the capacitance or other noise affects that has causeddifficulties with other types of sensors; and (3) the metering criteriais partly determined by a statistical base to compensate more readilyfor variations from sample to sample.

Although a preferred embodiment has been described with someparticularity, many modifications and variations of the preferredembodiment can be made without deviating from the invention. Therefore,it is to be understood that, within the scope of the appended claims,the invention may be practiced other than as specifically described.

What is claimed is:
 1. A method of pumping liquid comprising the stepsof:sensing changes in the strain in a conduit carrying the liquid to bemeasured; pumping liquid through the conduit in a manner that causesstrain related to the flow of liquid under the control of the pump; andusing the sensed strain to detect the pumping of liquid to apredetermined point.
 2. A method according to claim 1 in which the stepof sensing changes in the strain includes the steps of:continuouslysensing pulses as the liquid moves through the conduit; sensing anincrease in the amplitude of the pulses indicating liquid is approachingthe pump; and counting pulses during higher amplitude pulse reception.3. A method according to claim 2 further including the stepsof:determining the first presence of higher amplitude pulses; sensinggaps in the pulses; counting pulses between the start of pulses and thegap, and if said counted pulses between the start of pulses and the gapexceed a predetermined number of pulses, adding a count of pulses.
 4. Amethod according to claim 3 further including the step of determiningthe distance away from the roller of the pump at which a signal of highenough amplitude to indicate liquids are received for different heads ofliquid being drawn through the conduit.
 5. A method according to claim 3in which the step of adding a count of pulses includes the step ofadding a count of pulses controlled by a sensor which detects cycles ofthe pump directly from the pump.
 6. A method according to claim 5including the steps of:counting cycles of the pump as the pump pumps ina forward direction; detecting when liquid approaches the pump; usingsaid number of cycles of the pump between the time it begins pumpingliquid through the conduit to the pump until it senses a change inamplitude indicating liquid approaching the pump and using said count toobtain an indication of the head of pressure; using the indication of ahead of pressure to access statistical data indicating the amount ofpumping necessary to pump a predetermined amount of sample; pumping anumber of cycles sufficient to deposit the predetermined amount ofliquid in a container and then reversing the direction of pumping.
 7. Amethod according to claim 1 further including the step of:determiningthe first presence of higher amplitude pulses; sensing gaps in thepulses; counting pulses between the start of pulses and the gap wherebyat least one count of pulses is obtained; and adding at least certain ofsaid counts of pulses if there are plural counts of pulses.
 8. A methodaccording to claim 7 in which the step of adding a count of pulsesincludes the step of adding a count of pulses controlled by a sensorwhich detects cycles of the pump directly from the pump.
 9. A methodaccording to claim 8 including the steps of:counting cycles of the pumpas the pump pumps in a forward direction; detecting when liquidapproaches the pump; using said number of cycles of the pump between thetime it begins pumping liquid through the conduit to the pump until itsenses a change in amplitude indicating liquid approaching the pump andusing said count to obtain an indication of the head of pressure; usingthe indication of a head of pressure to access statistical dataindicating the amount of pumping necessary to pump a predeterminedamount of sample; pumping a number of cycles sufficient to deposit thepredetermined amount of liquid in a container and then reversing thedirection of pumping.
 10. A method of pumping liquid comprising thesteps of:sensing changes in the strain in a conduit carrying the liquidto be measured; pumping liquid through the conduit in a manner thatcauses strain related to the flow of liquid under the control of thepump; using the sensed strain to detect the pumping of liquid to apredetermined point; the step of sensing changes in the strain includingthe steps of continuously sensing pulses as the liquid moves through theconduit; counting the pulses; sensing gaps in the pulses; and countingpulses between a predetermined count of pulses and the gap, and if saidcounted pulses between the start of pulses and the gap exceed apredetermined number of pulses, adding a count of pulses; the step ofadding a count of pulses including the step of adding a count of pulsescontrolled by a sensor which detects cycles of the pump directly fromthe pump.
 11. A method according to claim 10 including the stepsof:counting cycles of the pump as the pump pumps in a forward direction;detecting when liquid approaches the pump; using said number of cyclesof the pump between the time it begins pumping liquid through theconduit to the pump until it senses a change in amplitude indicatingliquid approaching the pump and using said count to obtain an indicationof the head of pressure; using the indication of a head of pressure toaccess statistical data indicating the amount of pumping necessary topump a predetermined amount of sample; pumping a number of cyclessufficient to deposit the predetermined amount of liquid in a containerand then reversing the direction of pumping.
 12. A method according toclaim 1 including the steps of:counting cycles of the pump as the pumppumps in a forward direction; detecting when liquid approaches the pump;using said number of cycles of the pump between the time it beginspumping liquid through the conduit to the pump until it senses a changein amplitude indicating liquid approaching the pump and using said countto obtain an indication of the head of pressure; using the indication ofa head of pressure to access statistical data indicating the amount ofpumping necessary to pump a predetermined amount of sample; pumping anumber of cycles sufficient to deposit the predetermined amount ofliquid in a container and then reversing the direction of pumping.
 13. Amethod of metering a predetermined amount of sample of liquid comprisingthe steps of:measuring strain in a pump conduit to determine the numberof pump cycles necessary for liquid to reach a predetermined location ina conduit as it pumps to that location; using said number of pump cyclesto access a statistical base indicating a criteria for the number ofpump cycles necessary to deposit said predetermined amount of sample;and pumping for the predetermined number of pump cycles to deposit saidsample and reversing the direction of pumping after said sample isdeposited.
 14. A method according to claim 13 further including the stepof preparing a statistical base;said step of preparing said statisticalbase including the step of making a number of runs to determine thenumber of pulse counts with predetermined lengths of conduit whichcorrelate to a given pressure head as a statistical average; making anumber of predetermined runs which correlate length and inner diameterof conduit for a number of pump cycles to deposit a predetermined amountof liquid in a container from a given location on the conduit; findingstatistical averages and preparing a table so that the number of countsto a predetermined location provides a signal which may be used todetermine in a second statistical base the number of pump cyclesnecessary to deposit said predetermined sample.
 15. An apparatus forpumping liquid comprising:means for sensing changes in the strain in aconduit carrying the liquid to be measured; means for pumping liquidthrough the conduit in a manner that causes strain related to the flowof liquid under the control of the pump; means for using the sensedstrain to measure the pumping of a predetermined amount of liquid; themeans for sensing changes in the strain including means for continuouslysensing pulses as the liquid moves through the conduit; means forsensing an increase in the amplitude of the pulses indicating liquid isapproaching the pump; and means for counting pulses during higheramplitude pulse reception.
 16. An apparatus according to claim 15further including:means for determining the first presence of higheramplitude pulses; means for sensing gaps in the pulses; means forcounting pulses between the start of pulses and the gap; and means foradding certain of said count of pulses.
 17. An apparatus according toclaim 16 in which the means for adding a count of pulses includes themeans for generating pulses related to cycles of the pump, sensor meansfor sensing liquid in a conduit and means for counting said pulsesrelated cycles of the pump during at least a part of time that saidsensor means senses liquid.
 18. Apparatus according to claim 17including:means for counting cycles of the pump as the pump pumps in aforward direction; means for detecting when liquid approaches the pump;means for using said number of cycles of the pump between the time itbegins pumping liquid through the conduit to the pump until it senses achange in amplitude indicating liquid approaching the pump; means forusing said count to obtain an indication of the head of pressure; meansfor using the indication of a head of pressure to access statisticaldata indicating the amount of pumping necessary to pump a predeterminedamount of sample; means for pumping a number of cycles sufficient todeposit the predetermined amount of liquid in a container; and means forreversing the direction of pumping.
 19. An apparatus for pumping liquidcomprising:means for sensing changes in the strain in a conduit carryingthe liquid to be measured; means for pumping liquid through the conduitin a manner that causes strain related to the flow of liquid under thecontrol of the pump; means for using the sensed strain to measure thepumping of a predetermined amount of liquid; means for determining thefirst presence of higher amplitude pulses; means for sensing gaps in thepulses; means for counting pulses between the start of pulses and thegap; and means for adding certain of said count of pulses.
 20. Apparatusaccording to claim 19 in which the means for adding a count of pulsesincludes the means for adding a count of pulses controlled by a sensorwhich detects cycles of the pump directly from the pump.
 21. Anapparatus for pumping liquid comprising:means for sensing changes in thestrain in a conduit carrying the liquid to be measured; means forpumping liquid through the conduit in a manner that causes strainrelated to the flow of liquid under the control of the pump; means forusing the sensed strain to measure the pumping of a predetermined amountof liquid; means for counting cycles of the pump as the pump pumps in aforward direction; means for detecting when liquid approaches the pump;means for using said number of cycles of the pump between the time itbegins pumping liquid through the conduit to the pump until it senses achange in amplitude indicating liquid approaching the pump and means forusing said count to obtain an indication of the head of pressure; meansfor using the indication of a head of pressure to access statisticaldata indicating the amount of pumping necessary to pump a predeterminedamount of sample; means for pumping a number of cycles sufficient todeposit the predetermined amount of liquid in a container and thenreversing the direction of pumping.
 22. Apparatus according to claim 16further including a means for determining the distance away from theroller of the pump at which a signal of high enough amplitude toindicate liquids are received for different heads of liquid being drawnthrough the conduit.
 23. Apparatus for metering a predetermined amountof sample of liquid comprising:means for measuring strain in a pumpconduit to determine the number of pump cycles necessary for liquid toreach a predetermined location in a conduit as it pumps to thatlocation; means for using said number of pump cycles to access astatistical base indicating a criteria for the number of pump cyclesnecessary to deposit said predetermined amount of sample; means forpumping for the predetermined number of pump cycles to deposit saidsample; and means for reversing the direction of pumping after saidsample is deposited.
 24. Apparatus according to claim 23 furtherincluding:the means for preparing a statistical base; said means forpreparing said statistical base including means for making a number ofruns to determine the number of pulse counts with predetermined lengthsof conduit which correlate to a given pressure head as a statisticalaverage; means for making a number of predetermined runs which correlatelength and inner diameter of conduit for a number of pump cycles todeposit a predetermined amount of liquid in a container from a givenlocation on the conduit; means for finding statistical averages andpreparing a table so that the number of counts to a predeterminedlocation provides a signal which may be used to determine in a secondstatistical base the number of pump cycles necessary to deposit saidpredetermined sample.
 25. A method of pumping liquid comprising thesteps of:sensing changes in the strain in a conduit carrying the liquidto be measured; pumping liquid through the conduit with a peristalticpump whereby the conduit is strained by the strokes of the peristalticpump as the peristaltic pump cycles; counting the number of pump cyclesthat stress the conduit; and providing a warning signal to change theconduit when a predetermined number of pump cycles have been sensed. 26.A method according to claim 25 in which the step of sensing changes inthe strain includes the steps of:continuously sensing pulses as theliquid moves through the conduit; sensing an increase in the amplitudeof the pulses indicating liquid is approaching the pump; and countingpulses during higher amplitude pulse reception.
 27. A method accordingto claim 26 further including the step of:determining the first presenceof higher amplitude pulses; sensing gaps in the pulses; counting pulsesbetween the start of pulses and the gap; and if said counted pulsesbetween the start of pulses and the gap exceed a predetermined number ofpulses, adding a count of pulses.
 28. A method according to claim 27 inwhich the step of adding a count of pulses includes the step of adding acount of pulses controlled by a sensor which detects cycles of the pumpdirectly from the pump.
 29. A method according to claim 27 including thesteps of:counting cycles of the pump as the pump pumps in a forwarddirection; detecting when liquid approaches the pump; using said numberof cycles of the pump between the time it begins pumping liquid throughthe conduit to the pump until it senses a change in amplitude indicatingliquid approaching the pump and using said count to obtain an indicationof the head of pressure; using the indication of a head of pressure toaccess statistical data indicating the amount of pumping necessary topump a predetermined amount of sample; pumping a number of cyclessufficient to deposit the predetermined amount of liquid in a containerand then reversing the direction of pumping.
 30. A method according toclaim 29 further including the step of:determining the first presence ofhigher amplitude pulses; sensing gaps in the pulses; counting pulsesbetween the start of pulses and the gap; and adding certain of saidcount of pulses.
 31. A method according to claim 30 including the stepsof:counting cycles of the pump as the pump pumps in a forward direction;detecting when liquid approaches the pump; using said number of cyclesof the pump between the time it begins pumping liquid through theconduit to the pump until it senses a change in amplitude indicatingliquid approaching the pump and using said count to obtain an indicationof the head of pressure; using the indication of a head of pressure toaccess statistical data indicating the amount of pumping necessary topump a predetermined amount of sample; pumping a number of cyclessufficient to deposit the predetermined amount of liquid in a containerand then reversing the direction of pumping.
 32. A method according toclaim 31 including the steps of:counting cycles of the pump as the pumppumps in a forward direction; detecting when liquid approaches the pump;using said number of cycles of the pump between the time it beginspumping liquid through the conduit to the pump until it senses a changein amplitude indicating liquid approaching the pump and using said countto obtain an indication of the head of pressure; using the indication ofa head of pressure to access statistical data indicating the amount ofpumping necessary to pump a predetermined amount of sample; pumping anumber of cycles sufficient to deposit the predetermined amount ofliquid in a container and then reversing the direction of pumping.
 33. Amethod according to claim 25 including the steps of:counting cycles ofthe pump as the pump pumps in a forward direction; detecting when liquidapproaches the pump; using said number of cycles of the pump between thetime it begins pumping liquid through the conduit to the pump until itsenses a change in amplitude indicating liquid approaching the pump andusing said count to obtain an indication of the head of pressure; usingthe indication of a head of pressure to access statistical dataindicating the amount of pumping necessary to pump a predeterminedamount of sample; pumping a number of cycles sufficient to deposit thepredetermined amount of liquid in a container and then reversing thedirection of pumping.
 34. A method according to claim 25 wherein thereis a predetermined number of times the conduit is stressed for eachcycle of the peristaltic pump and the step of counting the pump cyclesthat stress the conduit includes the substeps of counting cycles in bothforward and reverse directions and providing a warning signal after apredetermined count.
 35. A method of pumping liquid comprising the stepsof:sensing changes in the strain in a conduit carrying the liquid to bemeasured; pumping liquid through the conduit in a manner that causesstrain related to the flow of liquid under the control of the pump;counting the number of pump cycles; measuring an amount of liquid pumpedto a predetermined point; the step of sensing changes in the strainincluding the steps of: continuously sensing first pulses as the liquidmoves through the conduit; sensing an increase in the amplitude of thefirst pulses indicating liquid is approaching the pump; and countingsecond pulses during the time the first pulses are at a higheramplitude.
 36. A method according to claim 35 further including the stepof:determining the first presence of higher amplitude first pulses;sensing gaps in the first pulses; counting second pulses between thestart of pulses and the gap; and if said counted pulses between thestart of pulses and the gap exceed a predetermined number of pulses,adding a count of pulses.
 37. A method according to claim 36 in whichthe step of adding a count of pulses includes the step of adding a countof pulses controlled by a sensor which detects cycles of the pumpdirectly from the pump.
 38. A method according to claim 37 including thesteps of:counting cycles of the pump as the pump pumps in a forwarddirection; detecting when liquid approaches the pump; using said numberof cycles of the pump between the time it begins pumping liquid throughthe conduit to the pump until it senses a change in amplitude indicatingliquid approaching the pump and using said count to obtain an indicationof the head of pressure; using the indication of a head of pressure toaccess statistical data indicating the amount of pumping necessary topump a predetermined amount of sample; pumping a number of cyclessufficient to deposit the predetermined amount of liquid in a containerand then reversing the direction of pumping.
 39. A method according toclaim 34 further including the step of:determining the first presence ofhigher amplitude pulses; sensing gaps in the pulses; counting pulsesbetween the start of pulses and the gap; and adding certain of saidcount of pulses.
 40. A method according to claim 39 in which the step ofadding a count of pulses includes the step of adding a count of pulsescontrolled by a sensor which detects cycles of the pump directly fromthe pump.
 41. A method according to claim 40 including the stepsof:counting cycles of the pump as the pump pumps in a forward direction;detecting when liquid approaches the pump; using said number of cyclesof the pump between the time it begins pumping liquid through theconduit to the pump until it senses a change in amplitude indicatingliquid approaching the pump and using said count to obtain an indicationof the head of pressure; using the indication of a head of pressure toaccess statistical data indicating the amount of pumping necessary topump a predetermined amount of sample; pumping a number of cyclessufficient to deposit the predetermined amount of liquid in a containerand then reversing the direction of pumping.
 42. A method according toclaim 41 in which the step of adding a count of pulses includes the stepof adding a count of pulses controlled by a sensor which detects cyclesof the pump directly from the pump.
 43. A method according to claim 42including the steps of:counting cycles of the pump as the pump pumps ina forward direction; detecting when liquid approaches the pump; usingsaid number of cycles of the pump between the time it begins pumpingliquid through the conduit to the pump until it senses a change inamplitude indicating liquid approaching the pump and using said count toobtain an indication of the head of pressure; using the indication of ahead of pressure to access statistical data indicating the amount ofpumping necessary to pump a predetermined amount of sample; pumping anumber of cycles sufficient to deposit the predetermined amount ofliquid in a container and then reversing the direction of pumping.